The standard C-Beam gantry plate will give you the most travel, but will provide the least support. The double wide ones give you better support in one axis (along the wheels) but not any better in terms of twist. The X-Large ones give you better twist, but the down side is that the wheels run along the outside of the C-Beam and not the inside. And it is easier to protect the inside from buildup of crud.

Do not use the universal ones, as the X-Large C-Beam ones are thicker and sturdier for C-Beams. The universal ones should be used if you are running a rail on one of the standard v-slot profiles.

For my router, I used double-wide gantry plates for all three axes. If I had it to do over, I would use double-wide for the Y and Z axes (along the edges and up and down). But I would use X-Large ones along the X axis for greater stiffness. The other nice thing about the X-Large ones for an X-Axis is that it will allow you to flip the whole thing over so that the lead screw or belt on the inside of the C-Beam points away from the Z-axis which is the part generating gunk.